1)
- Gut-Hacker has circular slash
- He makes a succefull counterattack.
- Is he allowed to attack again because he has circular slash?

2)Yes, it is allowed:
- Is he allowed to attack a other unit in range?

3)
- two hoplites fight against one gut-hacker
- hoplites have Defiance of Death
- 1 hoplite is dead but on the table because of Defiance of Death, the other hoplite lives
- Gut-Hacker attack the living hoplite
- Gut-Hacker hits
- Is the Gut-Hacker allowed to attack the the dead hoplite with Defiance of Death and when yes:
- is he allowed after a succefull attack on the dead hoplite with Defiance of Death to attack the living hoplite again?

Halodynes forever
Rules of DaricaThis is where we hold them! This is where we fight! This is where they die!

1. In the english rulebook Gut-Hackers have the tactic "circular slash". What is deadly strike? I guess you mean circular strike or there is a missprint somewhere.

2. Counter-attack is a passive activation, so ...

Rulebook page 71:

Counter attacking counts as a passive activation of the
model/unit and may be performed at any time during a round
and as often as the action tokens of the model or unit allow.During counter attacking (as with all passive activations),models may not move, use tactics, cast spells, shoot with missile weapons, or make any other form of action other than
performing melee attacks.

So all this is not valid (there is no "second target" and so on).

3. The dead hoplite may be targeted (because he is still on the table with 0 life points because defiance in death). But that does not matter since the rule for circular slash clearly states: "The Gut-Hacker may attack another model in close combat range until he misses or all models in melee range has been hit once.

By my understanding of the rules the guthackers benefit from the the Circular Slash tactic for the entire turn. Therefore, they benefit from the tactic even for passive activations and counterattacks (benefit from a tactic =/= use a tacitc). They should have multiple possible strikes as part of the same action via Circular Slash while counter attacking.

Also like Jendor of Threxia said, the Gut-Hackers can attack different unit models with his circular slash, as long as the model is in range and hasn't been hit before with this single (counter)attack.

Tactic rules replace normaly base rules, because thats a important thing about tactics. They give extra Bonus alongside the base rules. If the tactic says, you can attack other models in range, than it is allowed to attack the models in range without the restriction of counter attack rules.

What do you think about that?

I think, it also isnt the Intention of the game designer, that Gut-Hackers can attack an other unit with counterattack, but the rules allowed it.

Halodynes forever
Rules of DaricaThis is where we hold them! This is where we fight! This is where they die!

When I think about tactics, then I think about models performing a certain formation or mode of attack for a period of time. In our case of Guthackers they swing their weapons in circles for some time. Therefore, counterattacks should be swings in circles as well and hit multiple models (also other models that didnt trigger the counterattack). Rulebook says "all attacks made this way [circular slash] count as the same type and [now the important part] as part of the same action [counterattack] as the first attack made with circular slash".

By my interpretation it should be allowed, by my intuition it would be akward if it wouldnt.